Modern computer data storage systems, such as storage area networks (SAN) in enterprise environments often use the Fibre Channel (FC) network technology to provide high-speed (e.g., 2 to 32 gigabit/second) data transfers. A Fibre Channel network comprises a number of ports that are connected together, where a port is any entity that actively communicates over the network (either optical fiber or copper), where a port is usually implemented in a device such as disk storage or a Fibre Channel switch. The Fibre Channel protocol transports SCSI commands over Fibre Channel networks, and network topologies include point-to-point, arbitrated loop (devices in a ring), and switched fabric (devices/loops connected through switches).
A Fibre Channel port is generally any entity that actively communicates over the network and is usually implemented in a device such as disk storage, a Host Bus Adapter (HBA), network connection on a server, or a switch. Fibre Channel ports come in a variety of logical configurations. Common types of ports include N_Port (Node port), which is typically an HBA port that connects to an F_Port or another N_Port; F_Port (Fabric port), which is a switch port that is connected to an N_Port and connects the FC fabric to a node; or E_Port (Expansion port), which is a switch port that attaches to another E_Port to create an inter-switch link and is used to cascade FC switches together.
Fibre channel networks are often used to implement large-scale networks such as combined data center and storage networks. Such networks comprise at least two types of network traffic (e.g., data center and storage traffic) and a number of different host and target devices. Appropriate switches, known as Fibre Channel Forwarder (FCF) switches, are required to de-encapsulate and forward traffic to their respective networks. In typical FCF switches, the hosts and target must be connected to same switch or input/output module (IOM). Hosts generally cannot talk with targets present in different IOMs. This shortcoming has traditionally been addressed by using the E_Port (Expansion Port) mechanism within the Fibre Channel network topography. The E_Port mechanism, however, is generally a costly feature to include in a switch. Thus, many switches, such as inexpensive switches built for economy, do not provide E_Port functionality. For switches that do not have E_Port functionality, hosts cannot talk to targets that are not in the same switch.
What is needed, therefore, is a mechanism that allows hosts connected to one FCF switch to login to targets connected to different FCF switches without requiring the use of expansion or extender ports (E_Ports).
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